Pratt & Whitney's last radial piston engine was the 28-cylinder Wasp Major.
The largest piston engine the company produced, it displaced 4,360 cubic inches. Growth models developed ratings up to 4,300 horsepower.
The engine was configured with four rows of cylinders arranged in a spiral to enhance cooling. Its primary application was heavy transports and bombers. Four Wasp Majors powered Boeing's giant, double-decked Stratocruiser, the 377. An Air Force B-50, also powered by four Wasp Major engines, was the first airplane to fly nonstop around the globe, a feat made possible by aerial refueling.